The present application is related to German patent document No. 100 41 241.6 dated Aug. 22, 2000, which is hereby incorporated by reference in its entirety.
The invention relates to an aligning and feeding device intended for use in a device for the end-side processing of panel-shaped workpieces.
The problem of aligning panel-shaped or plate-shaped workpieces with the aim of directing them in the aligned state to end-side processing occurs in numerous functional circumstances. By way of example only, it is possible to refer to the processing of panel-shaped pieces of wood in a flat-dovetailing installation, in which the end sides of the pieces of wood are to be provided with a dovetail profile which extends in parallel to the base plane thereof and which is produced by milling. The exact production of the dovetail profile over the entire width of the wood is an essential prerequisite for the suitability of these pieces of wood for the end-side connection which is characterised by the engagement of adjacent dovetailed profiles. An erroneous alignment process causes the pieces of wood, which are to be connected on the end side, to be misaligned, i.e. they extend at angles with respect to each other.
The applicant has in-house knowledge of an aligning and feeding device which is characterised by a feed chain and which is characterised by a plurality of entrainers which are each disposed in pairs transverse to the feed direction at a spaced interval with respect to each other. The entrainers are disposed on individual chain members in such a way that they can be adjusted in the feed direction and are adjusted in a starting position under the proviso that their edges, which are intended to feed a piece of wood, extend in a common plane perpendicular to the feed direction. However, owing to unavoidable congestion during the production operation and owing to other disruptions, it is not possible to prevent individual entrainers from being maladjusted from the said position, which results in workpieces being misaligned and causes rejects during production.
It is the object of the invention to design an aligning and feeding device which is intended for use in a device for the end-side processing of panel-shaped workpieces and which renders it possible in a convenient manner to adjust the entrainers and to monitor the adjustment process including any subsequent adjustment operation. In the case of an aligning and feeding device of this type, this object is achieved by having at least one feed chain which is equipped with entrainers for the workpieces. The entrainers are each arranged in pairs on the feed chain at a spaced interval with respect to each other transverse to a feed direction. The entrainers can be adjusted in their position in the feed direction by means of an adjusting station for the purpose of aligning the position of the entrainers relative to an adjusting plane perpendicular to the feed direction. A measuring station is used for the contact-free detection of the positions of the entrainers relative to a measuring plane perpendicular to the feed direction. The measuring station and the adjusting station are disposed along a guide of the feed chain. The measuring station is arranged to generate measurement values for the purpose of describing the position of the entrainers relative to the measuring plane.
Accordingly, essential aspects of the invention include the arrangement of an adjusting station and a measuring station along the guide of the feed chain, wherein the measuring station is arranged to generate signals which describe the position of the entrainers relative to a measuring plane. While the adjusting station merely serves to adjust the position of the entrainers relative to an adjusting plane, i.e. on a frequent basis for manual alignment of the entrainers, the measuring station can be used for monitoring purposes and used in conjunction with a higher-ranking control for the purpose of visualising the adjustment state of all of the entrainers. At the same time, this renders it possible to identify the entrainer(s) which is/are currently maladjusted. One fundamental idea of the subject matter of the invention is thus to subject the adjustment state of entrainers to a permanent monitoring process during the operation of the device; so that disruptions in the form of maladjustments can be indicated and eradicated in a suitable manner. However, as an alternative to a continuous monitoring process it is also possible to check and log the adjustment state of all of the entrainers of the feeding device outside of the regular production operation of the device, i.e. in a separate measuring procedure. In each case, the adjustment position of the entrainers is monitored, which enables any deviations in position of the entrainers to be identified at the earliest possible point in time.
The adjusting station consists of a stop bar which can be moved into and removed from the feed path of the entrainers. The stop bar is provided in each case with stop bodies which lie in the adjusting plane and are intended to cooperate in each case with an entrainer pair. For example, the stop bodies are structurally formed by hemispherical stops which are adjusted in a precise manner relative to the stop bar, so that the entrainers which lie with their facing sides against these stops assume their desired position. One particularly advantageous embodiment of the stop bar resides in the fact that it can be pivoted about an axis extending in parallel with the feed direction, wherein the different pivot positions relative to this axis define the active and the inactive position of the feed bar. Accordingly, the latter can be pivoted manually about this axis between its two positions.
The measuring station which, corresponding to the entrainers arranged in each case in pairs, consists of two radiation barriers, e.g. light barriers which extend perpendicular to the feed direction and of which each is arranged for the purpose of generating a signal which indicates an interruption in the respective beam path. The measuring station is allocated an evaluating unit, in particular a control system, a computer or a comparable system, whose purpose is to evaluate the signals received by way of the light barriers and, whilst maintaining a desired level of measuring accuracy, to generate in the shortest time a signal which describes the adjustment state of the entrainers, where necessary an error signal. In practical terms, a tolerable deviation of the adjustment position of the entrainers is specified by the user, so that an error signal is produced in dependence upon a tolerance window. The radiation barrier used can be any system which consists of a transmitter and a receiver and whose functional principle is based upon the interruption of the beam path based between the transmitter and the receiver.
The two radiation barriers can essentially be disposed in a common plane perpendicular to the feed direction, wherein owing to the passage of the entrainers, in particular a time difference between the two passages, it is possible to use the points in time of the interruption of the beam paths to deduce the positions of the entrainers. However, with respect to lower assembly and adjusting outlay it is more advantageous if the two radiation barriers as seen in the feed directionxe2x80x94are disposed offset with respect to each other by a defined path element. This means that in the correctly adjusted state of two entrainers at a given speed the signals which are generated by the two beam paths are offset with respect to time and corresponding to this path element. This renders it possible to describe deviations from a desired position of the two entrainers by deviations from the value of a time difference and to generate error signals from these deviations according to a tolerance field which can be specified by the user.
Each evaluating unit is arranged to generate those signals which describe the deviation of the entrainer from a desired position and which also render it possible to identify the respectively measured entrainer, all of the information required for the subsequent adjusting process is available. This type of evaluation can be performed very rapidly, since by means of the evaluating unit 52 which is to be allocated to the measuring station, the required arithmetic procedures can run according to substantially shorter cycle times than those of a higher-ranking control system. In turn, this represents a significant contribution towards increasing the measuring accuracy. The use of a higher-ranking control system 54 for the purpose of implementing the arithmetic procedures associated with a measurement evaluation process would result in substantially longer measuring times in view of the cycle times which are required owing to the greater degree of complexity of the programmes installed in said control system.
The evaluating unit is operatively connected to the control system of the device by way of a suitable bus system. Within the framework of the aforementioned control system, it is possible randomly to evaluate, visualize and otherwise convert the signals generated by the measuring station.
The feeding speed of the feed chain is controllablexe2x80x94a condition which can be used in a particularly advantageous manner for the purpose of illustrating a measuring procedure, namely a complete revolution of the continuous-feed chain which is merely directed to measuring the adjustment position of the individual entrainers. Accordingly, it is possible for example to operate at a lower feeding speed for comparatively short path elements which correspond to the passage of the entrainers through the measuring station and also at a higher feeding speed. In this manner, it is possible to guarantee a high degree of measuring accuracy whilst at the same time limiting the time required for verifying the positions of all of the entrainers of a feed chain which is characterised by numerous pairs of entrainers.